1. Field of the Invention
When transporting ore and like bulk materials in a mine working, it is known to use electrically operated vehicles, so-called trolley vehicles. From a mechanical point of view, these may be designed as shown in FIG. 1 of the accompanying drawings) as a vehicle consisting of a traction unit 1 and a load-carrying unit 2, connected together via an arm 3 which is rigid in the vertical direction but rotatable in the lateral direction. An empty vehicle may have a weight of 30 tons and its load capacity may amount to 50 tons. Normally, the traction and load-carrying units are each provided with two wheels. The operation of the vehicle may take place by means of two electric motors, one in the traction unit and one in the load-carrying unit. The current supply to these motors normally takes place via a cable 4 and a current pick-up system 5 which includes one current collector for each of a plurality of conductors which, via isolators or otherwise, are suspended in a supply array 6 from the roof 7 of a heading in the mine.
The present invention relates to a method of and a device for automatically connecting and disconnecting the current collectors of a current pick-up system with current conductors of a supply array.
2. Description of the Prior Art
In the prior art arrangements, it is not at present possible to effect, in a simple manner, the connection of the current collectors of an electric trolley vehicle to the conductors of a supply array feeding it and located above the vehicle at any arbitrary location along the supply array. In the normal prior art arrangement connecting and disconnecting take place when the vehicle is stationary at special connection stations but otherwise connection/disconnection involves considerable mechanical work. One example of a known arrangement of a current collector pick-up system is illustrated in FIG. 2 of the accompanying drawings. In FIG. 2 the supply array 6 comprises four current collectors of which 8a, 8b and 8c constitute the phases of a three-phase supply to the vehicle and 8d constitutes a ground connection. The current collector pick-up system 5 is suspended from a guide rail 10 in the form of a T-bar and is guided thereon via wheels 9. The current supply from the current collector pick-up system to the trolley vehicle takes place via a mechanically reinforced cable 4 which at the same time hauls the current collector pick-up system 5 along the rail 10. The cable is suitably wound in a prestressed manner onto a cable winder 11 mounted on the vehicle. In such a design of current collector pick-up system, the system 5 is always guided via the wheels 9 engaging the guide rail 10. If the vehicle is driven in such a way that the mechanical stress in the current cable 4 becomes excessive, safety means is usually provided to effect a disconnection of the cable.
If the current collector pick-up system 5 as shown in FIGS. 1 and 2 should become jammed owing to downfalling ore, rock, and the like, this would involve an additional load on the cable winder 11 and the conductor cable 4 which, in an extreme case, might become torn away or disconnected, rendering the vehicle inoperable.
Other prior art arrangements are available but most of them are based on the principle described above and suffer from the same general disadvantages.
The connection between the current collector pick-up system and the suspension device, which--from the point of view of connecting and disconnecting--is, in principle, fixed in relation to the conductor system, undesirably restricts the freedom of movement of a trolley vehicle. In case of operational disturbances and faults of various kinds, it is desirable to be able to rapidly disconnect a vehicle from the supply array 6 and drive the vehicle away to some central collecting point or repair shop. A facility for easy connection/disconnection is thus highly desirable.
Because of the limited cross-section available in a mine heading, which in a typical case may amount to no more than about 25 m.sup.2 (5.times.5 m), current collection via a pantograph system as used, for example, in trains and other railbound vehicles, cannot be used. Since the trolley vehicles under discussion are provided with insulating rubber wheels, the ground on which they run cannot be used as a return conductor. The smallest number of overhead conductors, in the case of DC supply, will be two and in the case of an AC supply it will be three. For a three phase AC supply four conductors are needed. Thus it is not practicable to use the current collector pantograph system developed for electric trains.